It is known that stay bars may be secured in bore holes by means of polyester resins. Other resins which have been proposed for this purpose are polyurethane resins. The components from which these polyurethanes are formed are contained in a two-compartment cartridge, a polyisocyanate being contained in one of the compartments and a polyol in the other compartment. By destroying the cartridge with the stay bar introduced by rotation into the bore hole, the two components are intimately mixed to form the polyurethane. However, the rate at which this reaction progresses until complete hardening is obtained is very slow so that, after destruction of the cartridge and intensive mixing, the resin only gels after about 2 hours and only hardens after from about 5 to 6 hours (German Auslegeschrift No. 1,205,038 and British Patent No. 1,275,941). This long hardening time is a disadvantage so far as the installation of stays is concerned because the stay in question cannot, as desired, be immediately subjected to loads.
Although it would be possible to reduce the hardening time of polyurethane resins by adding accelerators to the polyol component, this measure would be attended by other disadvantages. On the one hand, the hardening time is dependent to a very large extent upon the quantity of accelerator used so that by adding small quantities of accelerators, for example certain organometallic compounds, it would only be possible to obtain an insignificant reduction in the hardening time. When relatively large quantities of accelerator are added, however, it has been found that these compounds undergo considerable decomposition and, as a result, soon lead, for example after storage for a few weeks, to the ineffectiveness of the cartridges outweighing the short hardening time required.
An object of the present invention is to enable stay bars to be secured in bore holes by means of polyurethane resins which harden extremely quickly, the gelling and hardening time together actually amounting to less than about 1 minute.
According to the present invention, this object is achieved by virtue of the fact that a polyol or mixture of polyols containing tertiary amine nitrogen of the type described in detail below is used as the polyol component in a two-compartment cartridge.